The thrust zone of the Ligurian Penninic Basal Contact (Monte Fronté, Ligurian Alps, Italy) Matteo Maino and Silvio Seno University of Pavia, Department of Earth and Environmental Sciences , via Ferrata, 1, 27100, Pavia, Italy 397000E 398000E 399000E 400000E 401000E 402000E 403000E 4°W W 0°E 4°E 8°E DB a 46°N 30 i 55 1200 San Bernardo c s o 16 r r a di Mendatica A 50°N b Mt. Saccarello q Regione e t 1300 n 2201 e - Ormea r 48°N Southalpine 2100 15 r FRANCE 22 o Germany Piemonte q T 2000 SMF Cima di Garlenda 1800 Aosta 40 1700 2142 SP 2 1900 10 18 1800 France 48°N 46°N 16 Cima Valletta 20 70 30 1900 2064 Austria 21 Switzerland BOR 45 30 16 B’ q SBF o 2000 20 PBC l 25 MFT l 9 Internal e 46°N r a Torino 4879000N n Rifugio Sanremo a Western Alps T 20 44°N TH-M e t n e 45°N r 34 r Italy o 55 1400 30 T Mt. Fronté Briançon 1700 35 A’ 2152 b 44°N Po Plain 24 16 q 40 42°N EB 35 2100 14 Gap 40 10 Spain 38 5 2000 25 q Mt. Cimanasso 12 PB SMF TPB 44 TOM W 0°E 4°E 8°E 12°E 1600 20 6 1900 E-U 15 A) Location of the study area in Western Europe. Cuneo 15 Passo di Garlenda PBC 1800 Colle della Melosa - 30 6 1500 B) Tectonic sketch of the Western and Ligurian Alps. Ligurian Alps 14 30 Pigna TOM SBF 1700 The yellow box shows the location of the Monte Fronté thrust zone along the EB 26 40 External MFT 60 20 Penninic Basal Contact (PBC). DB: Dent Blanche nappe (Austroalpine); E-U: 35 28 EB Rocca Rossa 65 Western Alps PB 60 Embrunais-Ubaye nappes; HF: Helminthoid Flysch nappes; TH-M: Torino hill Main Map 44°N ITALY HF q 4878000N 1600 and Monferrato high; TPB: Tertiary Piedmont Basin. EB 25 36 4 1600 SBF q 16 12 San 30 60 Nice 30 Ligurian EB 50 30 Remo TOM q 50 28 SBF Sea 36 14 45 20 1500 0 km 20 6°E 7°E 8°E TOM UF 40 40 EB Rocca 1700 EB 20 18 55 48 34 1400 Barbone TOM SBF EB Colle di Garezzo EB 28 PB EB Verdeggia 30 JL 18 45 DAUPHINOIS DOMAIN AND FORELAND BASIN SUCCESSION 25 PB 45 LEGEND 1500 SP JL RBT 40 q 35 1800 Exotic Blocks (EB) - Megablocks of Jurassic limestones, Late UF 28 1840 EB 38 Quaternary deposits (q) 1300 Cretaceous marly limestones and Eocene nummulitic limestones 1400 20 1300 30 Cima dell’Ortica (Jurassic-Eocene) 1200 28 Passo della Regione 30 RBT Rocca Goina SAN REMO - MONTE SACCARELLO UNIT - Helminthoid Flysch nappe 1100 Triora Olistostrome Member (TOM) - quartz-muscovitic Guardia EB Liguria 30 San Remo Flysch (SMF) - Calcareous limestones and marls sandstones and pelites with paraconglomerates 1200 PB 60 BOR TOM 22 (Upper Campanian-Maastrichtian) (Priabonian-Early Oligocene ?) 34 q 36 TOM EB Bordighera Sandstones (BOR) - quartz-feldspatic sandstones Ventimiglia Flysch (VF) - quartz-muscovitic sandstones and 4877000N MFT 12 (Upper Campanian-Maastrichtian) pelites (Priabonian-Early Oligocene ?) 20 25 32 Nummulitic Sandstones and Blue Marls (NS) - Nummulites-rich VF 44 San Bartolomeo Formation (SBF) - varicoloured pelites 22 1100 10 35 a 20 n EB limestones and Globigerina marls (Lutetian-Lower Priabonian) i (Upper Hauterivian-Upper Campanian) t n q e 15 1000 g EB r EB SBF A - marly limestones and marls e ROCCA BARBONE UNIT - Briançonnais domain Trucco Limestones (TL) t n e r 20 28 (Late Cretaceous) r 16 o EB - Megablocks of Late Cretaceous-Paleocene T EB SP 89 Exotic Blocks (EB) 40 marly limestones and Eocene nummulitic limestones 30 Symbols Fault SP 81 (Late Cretaceous-Eocene) A EB 34 MFT Bedding Monte Fronté Thrust 34 Triora Olistostrome Member (TOM) - quartz-muscovitic EB q sandstones and pelites with paraconglomerates 18 Overturned bedding RBT Rocca Barbone Thrust B 1000 (Priabonian-Early Oligocene ?) NS Goina EB A A’ Section line EB Cima di Bareghi - breccias with Mesozoic carbonate 17 Foliation 26 Polygenetic Breccias (PB) Realdo 24 1387 clasts and nummulitid fragments (Middle-Late Eocene) 900 International boundary 4876000N 22 Fold axis (syncline) EB 32 q 900 EB EB Upega Fm. (UF) - marly limestones and marls (Late Cretaceous) Peak / pass TL EB Triora 8 Fold axis (anticline) Rio di Nava and Val Tanarello Limestones (JL) - dark and light Settlement The map is referred to the WGS-1984 geographic coordinate system grey limestones (Middle - Late Jurassic) Stratigraphic boundary 0 250 metres 750 1000 (dashed is uncertain) SP 2 Road San Pietro dei Monti Dolostones (SP) - dolostones and limestones (Middle Triassic) Thrust River The lithological symbols used in the cross-sections are reported in the bottom-right corners of the legend boxes A A’ B B’ SSW NNE Road Mt. Fronté ridge SSW Road Rocca Barbone Rocca Rossa Rifugio Sanremo NNE 2100 2100 2000 2000 1900 1900 MFT 1800 1800 1700 1700 metres 1600 MFT metres 1600 1500 1500 RBT RBT 1400 1400 1300 1300 1200 1200 1100 1100 1000 2000 3000 4000 1000 2000 3000 4000 5000 6000 metres © Journal of Maps, 2016 metres.